The effect of jasplakinolide on the thermodynamic properties of ADP.BeF(x) bound actin filaments.

The effect of BeF(x) and a natural toxin (jasplakinolide) was examined on the thermal stability of actin filaments by using differential scanning calorimetry. The phosphate analogue beryllium fluoride shifted the melting temperature of actin filaments (67.4 degrees C) to 83.7 degrees C indicating that the filaments were thermodynamically more stable in their complex with ADP.BeF(x). A similar tendency was observed when the jasplakinolide was used in the absence of BeF(x). When both the ADP.BeF(x) and the jasplakinolide bound to the actin filaments their collective effect was similar to that observed with ADP.BeF(x) or jasplakinolide alone. These results suggested that ADP.BeF(x) and jasplakinolide probably stabilize the actin filaments by similar molecular mechanisms.